Fix some Rubocop offences & warnings in AWS config
Fix some Rubocop offences & warnings in AWS config

I was seeing the following locally:

* Layout/IndentationWidth
* Layout/ElseAlignment
* Lint/EndAlignment

For some reason these were not picked up by the Jenkins CI build of the
master branch. I plan to investigate why this didn't happen separately.

alphagov/asset-manager,alphagov/asset-manager,alphagov/asset-manager